golangci/golangci-lint · error

unsupported configuration format

Error message

unsupported configuration format

What it means

`validateConfiguration` (pkg/commands/config_verify.go:73) only knows how to decode `.yaml`, `.yml`, `.json` and `.toml` configuration files; anything else falls into the `default` branch and returns this error. It means the extension of the target file passed to config validation is not a supported format, so no decoder exists for it.

Source

Thrown at pkg/commands/config_verify.go:73

	var m any

	switch strings.ToLower(filepath.Ext(targetFile)) {
	case ".yaml", ".yml", ".json":
		m, err = decodeYamlFile(targetFile)
		if err != nil {
			return err
		}

	case ".toml":
		m, err = decodeTomlFile(targetFile)
		if err != nil {
			return err
		}

	default:
		// unsupported
		return errors.New("unsupported configuration format")
	}

	return schema.Validate(m)
}

func printValidationDetail(cmd *cobra.Command, detail *jsonschema.OutputUnit) {
	if detail.Error != nil {
		data, _ := json.Marshal(detail.Error)
		details, _ := strconv.Unquote(string(data))

		cmd.PrintErrf("jsonschema: %q does not validate with %q: %s\n",
			strings.ReplaceAll(strings.TrimPrefix(detail.InstanceLocation, "/"), "/", "."), detail.KeywordLocation, details)
	}

	for _, d := range detail.Errors {
		printValidationDetail(cmd, &d)
	}
}

View on GitHub (pinned to ed7a235d2d)

Solutions

1. Rename the configuration file to use a supported extension: .golangci.yml, .golangci.yaml, .golangci.json, or .golangci.toml
2. Check the path/argument passed to the verify command — it may point at the wrong file
3. Convert the configuration content into one of the supported formats (YAML is the conventional choice)

Example fix

# before
mv .golangci.conf .golangci.yml   # .conf is unsupported
# after
mv .golangci.conf .golangci.yml

func hasSupportedConfigExt(path string) bool {
    switch strings.ToLower(filepath.Ext(path)) {
    case ".yaml", ".yml", ".json", ".toml":
        return true
    }
    return false
}
// guard: if !hasSupportedConfigExt(cfgPath) { ... }

func isSupportedConfigFile(path string) bool {
	ext := strings.ToLower(filepath.Ext(path))
	return ext == ".yaml" || ext == ".yml" || ext == ".json" || ext == ".toml"
}

When it happens

Trigger: Calling `golangci-lint config verify` or the internal `validateConfiguration` with a target file whose extension is not .yaml/.yml/.json/.toml — e.g. pointing at a .ini, .conf, extension-less file, or a `.golangci.json5`; also programmatic calls to validateConfiguration with a wrong path.

Common situations: Renaming the config file and losing/altering its extension; pointing verification at the wrong file (e.g. a Makefile or README); tools generating config with an exotic extension; case variants are handled (`filepath.Ext` result is lowercased), so only truly unknown extensions trigger it.

Related errors

• the configuration contains invalid elements
• the configuration contains invalid elements
• can't set severity rule option: no default severity defined
• severity should be set
• analyzer doesn't have settings

AI-assisted analysis of golangci/golangci-lint@ed7a235d2d (2026-09-02). Data as JSON: /api/errors/2ecafc5b652df623. Report an issue: GitHub.